panic: unaligned 64-bit atomic operation. Support 32-bit architectures too.

[compliment]

panic: unaligned 64-bit atomic operation

goroutine 489 [running]:
runtime/internal/atomic.panicUnaligned()
        runtime/internal/atomic/unaligned.go:8 +0x24
runtime/internal/atomic.Xadd64(0x2e4e7c4, 0x1, 0x0, 0x2d87600, 0x30a8d40)
        runtime/internal/atomic/asm_arm.s:233 +0x14
github.com/anacrolix/dht/v2.(*traversal).wrapQuery(0x2e4e784, 0xca9b00, 0x2ef6fa0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        github.com/anacrolix/dht/v2@v2.9.1/traversal.go:115 +0x44
github.com/anacrolix/dht/v2.(*traversal).run.func1.1(0x2f8b130)
        github.com/anacrolix/dht/v2@v2.9.1/traversal.go:156 +0x30
github.com/anacrolix/dht/v2.(*traversal).beginQuery.func1.1(0x0)
        github.com/anacrolix/dht/v2@v2.9.1/traversal.go:179 +0x98
github.com/anacrolix/dht/v2.(*Server).beginQuery.func1.1()
        github.com/anacrolix/dht/v2@v2.9.1/server.go:745 +0x24
created by github.com/anacrolix/dht/v2.(*traversal).run

[anacrolix]

Could you try the associated commit? Was this issue only present on arm, did you find anything else that didn't work?

I would welcome PRs to include CI for testing arm if you're interested.

[anacrolix]

go get github.com/anacrolix/dht/v2@fd60ad06b4827d42a76235103e88b20e633db27c should do what you need in your project for testing this.

[compliment]

Was this issue only present on arm?

According to atomic/#pkg-note-BUG it affects all 32-bit architectures. I can confirm the same on ARM and 386.

anacrolix/dht@fd60ad0 didn't fix it, same error with different line number.

example/torrent built for 386

panic: unaligned 64-bit atomic operation

goroutine 795 [running]:
runtime/internal/atomic.panicUnaligned()
	runtime/internal/atomic/unaligned.go:8 +0x2d
runtime/internal/atomic.Xadd64(0x9e321e4, 0x1, 0x0, 0x0, 0x0)
	runtime/internal/atomic/asm_386.s:107 +0x11
github.com/anacrolix/dht/v2.(*traversal).wrapQuery(0x9e321e4, 0x86c4250, 0x9c753c0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
	github.com/anacrolix/dht/v2@v2.9.2-0.20210509011734-fd60ad06b482/traversal.go:115 +0x52
github.com/anacrolix/dht/v2.(*traversal).run.func1.1(0x9c0e008)
	github.com/anacrolix/dht/v2@v2.9.2-0.20210509011734-fd60ad06b482/traversal.go:156 +0x35
github.com/anacrolix/dht/v2.(*traversal).beginQuery.func1.1(0x0)
	github.com/anacrolix/dht/v2@v2.9.2-0.20210509011734-fd60ad06b482/traversal.go:179 +0x93
github.com/anacrolix/dht/v2.(*Server).beginQuery.func1.1()
	github.com/anacrolix/dht/v2@v2.9.2-0.20210509011734-fd60ad06b482/server.go:745 +0x23
created by github.com/anacrolix/dht/v2.(*traversal).run
	github.com/anacrolix/dht/v2@v2.9.2-0.20210509011734-fd60ad06b482/traversal.go:164 +0x83

[anacrolix]

Could you provide the new stack trace? It's probably another atomic elsewhere in the package that also needs to be fixed.

[compliment]

@anacrolix You can build example/torrent from this repo itself for linux 386 and run it on amd64 or for linux arm and run it on arm64. I included the new stack trace for example/torrent from this repo itself in the previous comment.

[anacrolix]

Sorry I don't have the necessary platforms available. A PR to include those in CI is welcomed. It should be sufficient to move any stat blocks to the top of their structs, per some of the comments where I've done this previously.

[silentmurdock]

Hello!

I think I've managed to fix the problem with the help of this page: https://go101.org/article/memory-layout.html
I made a pull request for the dht v2.9.1 package.

I use anacrolix torrent for my torrent player application ( White Raven ) for Samsung Smart TV E, F, H series. Each of these televisions has armv7 and armv6 32-bit processors.

For me, this bug fix is necessary.

Tested on armv7 32-bit, windows 32-bit, linux 32-bit.

[anacrolix]

Interesting article. I take it then on a 32 bit system, the struct field alignment even of an int64 might be only 4 bytes.

[anacrolix]

See anacrolix/dht#46.